I do not think that we can say that this is DSB for sumps. The result may be the same - lower NO3 as rest product. But the biochemical pathways are different IMO. This is a fresh water system from the beginning. Fresh water aquarists believe that free NH3/NH4 will favors micro algae growth and NO2 is highly toxic for fresh water organisms. They need a fast method to take care of the NH3/NH4 and NO2. Maybe this can work in SW too but more observations and experiences is needed.
Sincerely Lasse
Agreed, thanks Lasse.